Apparatus for controlling variation in a characteristic of strand-like material

ABSTRACT

Apparatus for controlling variation in a characteristic such as denier or sliver weight of strand-like material. The apparatus includes means for fluidically monitoring the characteristic of the material as it passes therethrough. A fluidic bridge is responsive to the monitoring means and produces first and second pressure signals from respective first and second outputs when the monitored characteristic of the material has deviated from a nominal value beyond a respective high and low set predetermined limit. First and second pressure sensitive electrical switches are respectively fluidically coupled to the first and second outputs of the fluidic bridge and are actuated only in response to and for the duration of one of the first and second pressure signals. Means responsive to the actuation of the first and second switches are provided to cause drive means which communicate with the strand-like material to vary the characteristic of the strand-like material until the deviation of the characteristic of the material is confined between the high and low set predetermined limits.

United States Patent Bottone, Jr.

1 1 APPARATUS FOR CONTROLLING VARIATION IN A Cl-IARACTERISTIC OF Primary ExaminerGene Z. Rubinson Attorney, Agent, or FirmS. A. Young; P. L. Schlamp; R. G. Simkins Aug. 13, 1974 5 7 ABSTRACT Apparatus for controlling variation in a characteristic such as denier or sliver weight of strand-like material. The apparatus includes means for fluidically monitoring the characteristic of the material as it passes therethrough. A fluidic bridge is responsive to the monitoring means and produces first and second pressure signals from respective first and second outputs when the monitored characteristic of the material has deviated from a nominal value beyond a respective high and low set predetermined limit. First and second pressure sensitive electrical switches are respectively fluidically coupled to the first and second outputs of the fluidic bridge and are actuated only in response to and for the duration of one of the first and second pressure signals. Means responsive to the actuation of the first and second switches are provided to cause drive means which communicate with the strand-like material to vary the characteristic of the strand-like material until the deviation of the characteristic of the material is confined between the high and low set predetermined limits.

10 Claims, 4 Drawing Figures PATENIED AUG 1 3 I974 J AC SUPPLY IIO FIG. 4

APPARATUS FOR CONTROLLING VARIATION IN A CHARACTERISTIC OF STRAND-LIKE MATERIAL BACKGROUND OF THE INVENTION 1. Field Of The Invention This invention relates to apparatus for controlling variation in a characteristic such as diameter, denier or sliver weight of strand-like material of the type including yarn, fiber or the like.

2. Description Of The Prior Art In the past a manually operated system was used to control a characteristic such as a diameter, denier or sliver weight of continuously moving strand-like material such as yarn. A pneumatic sensor head monitored deviations in the characteristic of the yarn as it passed through the sensor head. The sensor head was part of a pneumatic fluidic bridge which produced first and second output pressure signals when the characteristic in the yarn deviated from a nominal value beyond a higher and lower predetermined value. The first and second output pressure signals were used to actuate a visual indication. Upon observing the visual indication, an operator turned a manual control for a standard SCR speed motor controller, which in turn varied the output speed of a motor. The output shaft of the motor was mechanically coupled to variable speed drive rolls which engaged the continuously moving strand-like material and varied the characteristic of the strand-like material to within the permissible limits.

Such a technique for controlling the characteristic of continuously moving strand-like material is to say the least, not very precise, and is also expensive since it requires the use of an individual to observe a digital error signal and make an analog error correction. This manual type error correction can in some instances lead to sluggish control over deviation in the characteristic of the strand-like material, and in other instances lead to excessive over corrections in the characteristic of the material.

OBJECTS OF THE INVENTION It is therefore an object of this invention to provide an improved system for automatically controlling variation in a characteristic of continuously moving strandlike material.

It is another object of this invention to provide an apparatus for automatically converting a digital error signal, which is representative of a sensed variation in a characteristic of strand-like material, to an analog error signal in order to correct the deviation in the characteristic of the material.

Other objects of the invention will be pointed out and understood hereinafter.

SUMMARY OF THE INVENTION In accordance with a broad aspect of the invention there is provided an apparatus for controlling variation in a characteristic of continuously moving strand-like material such as yarn wherein the characteristic being monitored may be the sliver weight or denier of the material. The apparatus is comprised of a fluidic device for monitoring the characteristic of the strand-like material as the material passes through the device. The fluidic device is part of a fluidic bridge, which bridge produces output pressure signals when predetermined variations in the characteristic of the material is monitored. The output pressure signals cause the actuation of pressure sensitive electrical switches, wherein the actuated switches in turn cause the actuation of a stepping motor. The output drive shaft of the stepping motor rotates the arm of a potentiometer so as to change the value of its resistance. A motor speed control SCR circuit responds to the changing resistance of the potentiometer and causes a variation of the output shaft speed of a drive motor. The variation in output shaft speed of the drive motor changes the surface speed of drive rollers which are in contact'with the continuously moving strand-like material so as to vary the characteristic of the strand-like material until the characteristic as monitored by the fluidic device is within a range of permissible predetermined values. When this happens, the pressure sensitive switches open and the stepping motor is turned off so that no further variation in speed of the drive motor occurs.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram of the apparatus for controlling variation in a characteristic of continuously moving strand-like material;

FIG. 2 is a pneumatic circuit for actuating the pressure sensitive electrical switches;

FIG. 3 is the electrical circuit for driving the stepping motor; and

FIG. 4 is a simplified speed control circuit for varying the output shaft speed of the drive motor.

DESCRIPTION OF A PREFERRED EMBODIMENT The apparatus for controlling variation in a characteristic of continuously moving strand-like material will now be explained with reference to FIG. 1. The continuously moving strand-like material 10 may be in the form of yarn, fabric, filament, wire, or other types of similar materials, and the characteristic which is to be controlled may be the denier, sliver density, fabric porosity, filament diameter, material thickness, depth, weight, etc., of the material. Strand-like material 10, which is moving in the direction of the arrow as shown in FIG. 1, passes through a means for fluidically monitoring a desired characteristic of the strand-like material. This fluidically monitoring means may be in the form of a fluidic device 12 such as a standard trumpet sensor or a fluidic gaging sensor head of the type described in US. Pat. No. 3,667,282, issued June 6, 1972 entitled Fluidic Gaging Sensor Head, inventors Bert J. Czwakiel and Donald F. Miller and assigned to the assignee of the present invention. Fluidic device 12 produces an output back pressure signal which is proportional to variation in the characteristic of the strand-like material which passes therethrough. A more detailed description of the actual operation of fluidic device 12 can be found in the above-referred to US.

Pat. No. 3,667,282. The output back pressure signal from fluidic device 12 is fluidically coupled to an instrument 14 which contains a fluidic bridge having a high output pressure, port and a low output pressure port. Also contained therein is a first pressure sensitive switch fluidically coupled to the low output pressure port and a second pressure sensitive switch fluidically coupled to the high output pressure port. A more detailed description of the fluidic circuit controlling the pressure sensitive switches will be made later. First and second pressure sensitive electrical switches are connected in circuit relationship with the windings of a bidirectional stepping motor 16. An output shaft 18 of motor 16 rotates at intervals determined by a timer switch 20. Shaft 18 is mechanically coupled to a moving arm 22 of a potentiometer 24. A more detailed description of the electrical circuit controlling the operation of bidirectional stepping motor 16 and potentiometeter arm 22 will be made later. Potentiometer 24 provides a variable resistance means which is in circuit relationship with a motor speed control circuit 26 that controls the speed of an output shaft 28 of a drive motor 30. Shaft 28 is mechanically coupled to a pair of variable speed drive rollers 32 which engage the continuously moving strand-like material. A constant speed drive motor 34 has its output drive shaft 36 mechanically coupled to a pair of constant speed drive rollers 38, which constant speed drive rollers also engage the continously moving strand-like material.

Referring now to FIG. 2, the fluidic circuit for actuating the pressure sensitive switches will now be described. A pressure source 40 supplies an unregulated pressure signal to a supply pressure regulator 42. Regulator 42 is adjustable and may be a standard fluid control valve. The regulated pressure signal from the output of regulator 42 is then fluidically coupled to a low set variable fluidic resistor 44, a sensor head adjust valve 46 and a high set variable fluidic resistor 48. Variable fluidic resistors 44 and 48 may be of the laminar type described in US; Pat. No. 3,532,127, issued Oct. 6, I970 entitled Variable Fluidic Resistor Device,

inventors Thomas H. Vogelsang and Salvatore Bottone, Jr. and assigned to the assignee of the present invention. Sensor head adjust valve 46, which may be any standard fluidic control valve, is used to set the pressure level of the fluid (gas) flowing into fluidic monitoring device 12. Low set variable fluidic resistor 44 is fluidically connected to one end of a fixed fluidic resistor 50, and variable fluidic resistor 48 is fluidically connected to one end of a fixed fluidic resistor 52. The respective opposite ends of fixed fluidic resistors 50 and 52 are bled to the atmosphere so that the combination of variable fluidic resistor 44 and fixed fluidic resistor 50, and the combination of variable fluidic resistor 48 and fixed resistor 52, each form an adjustable pressure divider at the junction of the fixed and variable resistors. By adjusting the value of variable fluidic resistor 44 a setting for a low pressure signal can be made at a first input 53 to a fluidic gain block 54, and likewise by adjusting the value of variable fluidic resistor 48 a setting for a high pressure signal can be made at a first input 55 of a fluidic gain block 56. The output pressure signal from fluidic monitoring device 12 is fluidically coupled to second inputs 53a and 55a of respective gain blocks 54 and 56. At this point it should be noted that fixed fluidic resistors 50 and 52 are of the same type as variable fluidic resistors 44 and 48, while gain blocks 54 and 56 are of the type described in US. Pat. No. 3,534,755, issued Oct. 20, I970 entitled High Signal To Noise Fluidic Amplifier and Fluidic Components, inventor Thomas F. Urbanosky and assigned to the assignee of the present invention. By utilizing well known fluidic engineering techniques the gain blocks can be so adjusted that if the back pressure signal from fluidic monitoring device 12 is less than the low set pressure signal at input 53 of gain block 54 then a signal from an output 57 of gain block'54 will actuate a first pressure sensitive electric switch 58, and if the back pressure signal from fluidic monitoring device 12 is greater than the high set pressure signal at output of gain block 56 then a signal from an output 59 of gain block 56 will actuate a second pressure sensitive electric switch 60, while if the back pressure signal is equal to or greater than the low set pressure signal and equal to or less than the high set pressure signal, the signals at the respective outputs of gain blocks 54 and 56 will not be sufficient to actuate either of pressure sensitive switches 58 and 60. Pressure sensitive electrical switch 58 in this example is comprised of a normally closed electrical switch 62 which opens when the pressure sensitive switch is actuated, and a normally open electrical switch 64 which closes upon actuation of pressure sensitive switch 58. Similarly, pressure sensitive switch is comprised of a normally closed electrical switch 66 which opens when pressure sensitive switch 60 is actuated, and a normally open electrical switch 68 which closes upon actuation of pressure sensitive v switch 60.

In FIG. 3 switches 64 and 68 are shown in electrical circuit relationship with the windings of the above referred to bidirectional stepping motor 16. In this instance, normally closed electrical switches 66 and 62 are not utilized and there is no need to further discuss them. Now, referring to the circuit shown in FIG. 3, the positive (8+) terminal of a DC source of supply is connected in series with a manual ON-OFF switch 70 which may be mounted on a panel of instrument l4. ON-OFF switch 70 is connected in series with a timer switch 72 wherein timer switch 72 is basically a cyclic timer which is closed for a portion of a cycle and open for the remaining portion of the cycle. In this instance, the switch could be closed for thirty seconds or less and open for thirty seconds or more, while the whole cycle may be sixty seconds in duration. Timer switch 72 may be a standard off the shelf item such as the plug-in timers HGIOO series sold by Eagle Signal, a systems division of Gulf and Western Industries, Inc. and shown in its Bulletin 32l (l- 70-ES) or it may be a standard astable or pulsed monostable multivibrator which drives either a relay or an electronic switch such as a transistor. Timer switch 72 is connected in series with the anodes of respective blocking diodes 74 and 76. The cathode of blocking diode 74 is connected in series with a clockwise winding 78 of stepping motor 16, normally open switch 68 of pressure sensitive switch 60, a normally closed switch 80 of a limit switch 82 and circuit ground. The cathode of blocking diode 76 is connected in series with a counter-clockwise winding 84 of stepping motor 16, normally open switch 64 of pressure sensitive switch 58, a normally closed switch 86 of a second limit switch 88 and circuit ground.

When pressure sensitive switch 60 is actuated, normally open switch 68 closes and a lamp 90, which is connected in series with switch 68 and between the B+ terminal of a source of DC supply and circuit ground, lights up on the panel of instrument 14. The lighting of lamp 90 indicates that the characteristic of the strand- Iike material being monitored has varied above its predetermined high set limit and the system has begun to take corrective action to reduce the variation in the characteristic of the material to within permissible limits. With ON-OFF switch 70 and switch 68 closed, current flows through clockwise winding 78 of stepping motor 16 during each pulsed interval that timer switch 72 is closed so that the output shaft of stepping motor 16 rotates incrementally during each period that switch 72 is closed. Each time switch 72 opens, output shaft 18 of stepping motor 16 makes another equal incremental rotating movement and then stops to await the arrival of the next current pulse which occurs when the timer switch again closes. In this manner timer switch 72 causes a digital pulse, which is applied to the clockwise winding while switch 68 is closed, to be converted to an analog movement by the incremental output shaft rotation of bidirectional stepping motor 16.

Similarly when pressure sensitive switch 58 is actuated, normally open switch 64 closes so that a lamp 92, which is connected in series with switch 64 and between the B+ terminal of a DC power source and circuit ground, lights up and is visible on the panel of instrument 14. The lighting of lamp 92 indicates that the system has begun to take corrective action to reduce the variation in the characteristic of the material to within permissible limits. At this point it should be noted that output shaft 18 of motor 16 will be making incremental movements in either the clockwise or counter-clockwise direction of approximately 7 V2 for the duration of each current pulse passing through either of the windings and another 7 A? immediately after the cessation of each current pulse when motor 16 is a Bidirectional lS-Degree Stepping Motor, Series 9AL4/5 sold by Sigma Instruments, Inc. of Braintree, Massachusetts and described in their Bulletin RE-l l 1. Other suitable stepping motors could also be used.

Output shaft 18 of stepping motor 16 is so mechanically coupled to arm 22 of potentiometer 24 that as shaft 18 incrementally rotates counter-clockwise, potentiometer arm 22 is moved in a direction to increase the resistance of that portion of the potentiometer which is in circuit relationship with motor speed control circuit 26, and as shaft 18 incrementally rotates clockwise, potentiometer arm 22 is moved in the opposite direction so as to decrease the resistance of that portion of the potentiometer which is in circuit relationship with motor speed control circuit 26. When the potentiometer arm has been moved to a position where the maximum resistance of the potentiometer is in circuit relationship with circuit 26, then further counterclockwise rotation of shaft 18 may cause the destruction of the potentiometer. Similarly, when the potentiometer arm has been moved to a position where the minimum resistance of the potentiometer is in circuit relationship with control circuit 26, then further clockwise rotation of shaft 18 may cause the destruction of the potentiometer.

In order to avoid destruction of the potentiometer under the circumstance just described above, a disc 94 is mounted on or mechanically coupled to either drive shaft 18 or potentiometer arm 22, whereby this disc rotates whenever shaft 18 is rotating. First and second mechanical stops 96 and 98 are mounted on disc 94. First stop 96 is located in such proximity to limit switch 88 that as drive shaft 18 is rotating counterclockwise, and before the maximum potentiometer arm setting is reached, mechanical stop 96 will actuate limit switch 88. Actuation of limit switch 88 causes its normally closed switch 86 to open and the flow of current through counter-clockwise winding 84 to be interrupted so that shaft 18 stops rotating and does not destroy potentiometer 24. As limit switch 88 is actuated its normally open switch 100 closes. Normally open switch is in series with an alarm 102 which can be either a visual or audible alarm. In this example we will consider alarm 102 to be a visual type alarm, such as a lamp. The series combination of switch 100 and lamp 102 is connected across the B+ terminal of a DC supply and circuit ground so that upon actuation of limit switch 88 and the closure of its normally open switch 100, lamp 102 lights up so as to provide a warning that the maximum setting of the potentiometer has been reached, and further correction of the variation in the characteristic of the strand-like material to above its low set limit is not possible unless an adjustment is made in the motor speed control circuit. Likewise mechanical stop 98 is located on disc 94 in such proximity to limit switch 82 that as drive shaft 18 is rotating clockwise, and before the minimum potentiometer arm setting is reached, mechanical stop 98 will actuate limit switch 82. Actuation of limit switch 82 causes its normally closed switch 80 to open and the flow of current through clockwise winding 78 to cease so that shaft 18 stops rotating and does not destroy potentiometer 24. Furthermore upon actuation of limit switch 82 its normally open contact 104 closes. Normally open contact 104 is in series with an alarm 106 which alarm can be either visual or audio, and again in this example we will assume that it is an visual alarm, such as a lamp. The series combination of switch 104 and lamp 106 also is connected across the B+ terminal of a DC power source and circuit ground, so that upon the closing of contact 104 the lamp lights up so as to provide a visual indication that a minimum setting of the potentiometer has been reached, and further correction of the variation in the characteristic of the strand-like material to below its high set limit is not possible unless an adjustment is made in the motor speed control circuit.

As shown in FIG. 4, potentiometer 24 is in electrical circuit relationship with one example of a motor speed control circuit. In this instance one terminal 108 of the potentiometer is electrically connected to the cathode of a blocking diode 110, and the anode of diode 110 is electrically connected to one terminal of a source of AC power. The other terminal 112 of potentiometer 24 remains unconnected. A movable electrical contact 114 of potentiometer 24 is mechanically coupled to arm 22 and electrically coupled to the juncture between a gateterminal of a Silicon Controlled Rectifier 116 and one terminal of a charging capacitor 118. The other terminal of capacitor 118 and a cathode of SCR 116 are connected to the other terminal 'of the AC supply, while an anode of SCR 116 is connected to the anode of diode 110 via a winding 120 of motor 30, and in this instance motor 30 is a DC motor. As contact 114 moves toward terminal 112 the resistance in series with capacitor 118 increases, and similarly as contact 114 is moved towards terminal 108 the resistance in series with capacitor 118 decreases. In operation during the positive half of a single cycle of the AC signal applied across the anode and cathode of the SCR, capacitor 118 begins to charge through diode 110 and that portion of the resistance of potentiometer 24 between terminal 108 and its movable contact 114. As soon as capacitor 118 charges to the gate to cathode firing voltage of SCR 116, the SCR fires and current passes through winding 120 of motor 30 for the remainder of the positive half of the cycle. After SCR 116 fires and while it is ON", capacitor 118 discharges through the gate to cathode of the SCR. As soon as the AC voltage returns to zero, SCR 116 turns off and the current through winding 120 of motor 30 ceases. During the negative half of the AC cycle, diode 110 is in the blocking condition and it therefore prevents capacitor 118 from charging. Now when the positive half of the next 'cycle begins, capacitor 118 again begins to charge and SCR 116 fires at approximately the same time or angle in the cycle. At this firing angle, output shaft 28 of motor 30 attains a specified speed, and in turn drives variable speed rollers 32 so that the combination of the surface speed of variable speed rollers 32 and constant speed rollers 38 determines the characteristic of the strand-like material. At this point it should be noted that motor speed control circuits other than the one just described, such as circuits found in any General Electric SCR or Transistor Manual can be easily I adapted for use in the system described in this invention. Furthermore, there are also many commercially available motor speed controllers'which are purchasable as off the shelf items and which can be interconnected with potentiometer 24 to operate in the described manner in accordance with this invention.

For the purpose of describing the operation of the above system, the characteristic of the strand-like material which is to be controlled is assumed to be sliver weight. The back pressure of fluidic device 12 is first adjusted for a corresponding nominal sliver weight. Then the back pressure of fluidic device 12 is measured for the maximum and minimum allowable sliver weight. The high pressure set limit at input 55 of gain block 56 is set (by adjusting resistor 48) to equal the pressure at input 55a of gain block 56 which corresponds to the maximum allowable sensed sliver weight. The low pressure set limit at input 53 of gain block 54 is also set (by adjusting resistor 44) to equal the pressure at input 53a of gain block 54 which corresponds to the minimum allowable sensed sliver weight.

As the strand-like material is being continuously monitored, if the sliver weight of the material increases above the maximum allowable limit, the output pressure signal from fluidic device 12 exceeds the high pressure set limit at input 55 of gain block 56, thereby causing a pressure signal from output 59 of gain block 56 to actuate pressure sensitive switch 60. Normally open switch 68 then closes, causing the actuation of stepping motor 16 so that its output shaft 18 begins to rotate incrementally in the clockwise direction. The clockwise rotation of output shaft 18 causes potentiometer arm 22 to force movable electrical contact 114 toward terminal 108 so as to decrease the resistance in series with capacitor 118. The decrease in the resistance in series with capacitor 118 causes capacitor 118 to charge faster so that SCR 116 fires earlier in each cycle of the AC signal applied across the anode and cathode of the SCR, thereby increasing the duration of the current passing through winding 120 and also increasing the rotational speed of shaft 28 of motor 30. The increase in speed in shaft 28 causes drive rollers 32 to increase in speed relative to rollers 38, which in turn causes a decrease in the sliver weight of the strand-like material. Once the sliver weight of the strand-like ma-' terial decreases to or below its maximum allowable value, the back pressure signal from fluidic device 12 drops to or below the high pressure set limit, thereby resulting in deactuation of pressure sensitive switch 60 and discontinuation of any further change in the shaft speed of motor 30.

Similarly, if the sliver weight of the strand-like material drops below the minimum allowable limit, the output pressure signal from fluidic device 12 drops below the low pressure 'set limit at input 53 of gain block 54, thereby causing the actuation of pressure sensitive switch 58. Normally open switch 64 then closes, and current passes through counter-clockwise'winding'84 of bidirectional stepping motor 16. Output drive shaft 18 of motor 16 begins to rotate incrementally in the counter-clockwise direction, which causes potentiometer arm 22 to force movable electrical contact 114 toward terminal 112 of potentiometer 24. This movement causes an increase in the resistance in series with capacitor 118 and consequently an increase in the charging timeofcapacitor 118 so that SCR 116 fires later in each cycle of the AC signal applied across the anode and the cathode of the SCR, so as to decrease the duration of the current flowing through winding 120 and also decrease the speed of drive shaft 28 of DC motor 30. This decrease in speed of drive shaft 28 causes a corresponding decrease in the speed of variable speed drive rollers 32 relative to constant speed drive rollers 38, and thereby results in an increase in sliver weight of strand-like material. Once the sliver weight of the material increases to or above its minimum allowable value, the back pressure signal from fluidic device 12 increases to or above the low pressure set limit, thereby resulting in deactuation of pressure sensitive switch 58 and cessation in the variation in the speed of drive rollers 32. Drive rollers 32will then remain at a specified speed until the sliver weight of the strand-like material again varies outside of its high set and low set limits. It should be understood that the operation of the invention could just as easily been explained with reference to a characteristic of the strandlike material other than sliver weight.

Although the invention has been described with reference to a specific embodiment thereof, numerous modifications are possible without departing from the invention and it is desirable to cover all modifications falling within the spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for controlling variation and a characteristic of continuously moving strand-like material comprising: 7

a. means for fluidically monitoring the characteristic of the strand-like material passing therethrough;

b. a fluidic bridge responsive to said monitoring means for producing a first pressure signal from a first output when the monitored characteristic of the strand-like material deviates beyond a first predetermined value in a first direction;

c. a first pressure sensitive electrical switch fluidically coupled to said first output of said fluidic bridge and being actuated only in response to and for the duration of said first pressure signal;

d. drive means engaging the strand-like material; and

e. means responsive to the actuation of said first switch for causing said drive means to vary the characteristic of the strand-like material in a direction opposite to that of the first direction until the characteristic of the material no longer deviates beyond the first predetermined value, whereby said first pressure signal ceases, causing said first switch to become deactivated and said drive means to cease varying the characteristic of the material,

said responsive means including:

i. a motor having a shaft output drive, said shaft turning in a first rotational direction in response to actuation of said first switch;

ii. speed control means coupled to and controlling the speed of said drive means; and

iii. electrical means mechanically coupled to said shaft for varying the operation of said speed control means. 7

2. Apparatus for controlling variation in a character istic of continuously moving strand-like material according to claim 1 wherein said motor includes a field winding in series with said first switch.

3. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 2 further including a limit switch in series with said winding and said first switch.

4. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 3, wherein said electrical means includes a potentiometer having an input shaft mechanically coupled to said motor shaft.

5. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 4 further including:

a. a disc mechanically coupled to the movement of said motor shaft, said disc having a mechanical stop positioned thereon to engage and deactivate said limit switch and thereby deactivate said motor to prevent said motor shaft from turning said potentiometer shaft beyond a point determined by the position of said mechanical stop so as to prevent destruction of said potentiometer.

6. Apparatus for controlling variation in a characteristic of continuously moving strand-like material comprising:

a. means for fluidically monitoring the characteristic of the strand-like material passing therethrough;

b. a fluidic bridge responsive to said monitoring means for producing a first pressure signal from a first output when the monitored characteristic of the strand-like material deviates beyond a first predetermined value in a first direction, and for producing a second pressure signal from a second output when the monitored characteristic of the strand-like material deviates beyond a second predetermined value in a second direction;

c. a first pressure sensitive electrical switch fluidically coupled to said first output of said fluidic bridge and being actuated only in response to and for the duration of said first pressure signal;

d. a second pressure sensitive electrical switch fluidically coupled to said second output of said fluidic bridge and being actuated only in response to and for the duration of said second pressure signal;

c. drive means engaging the strand-like material; and

f. means responsive to the actuation of said first switch for causing said drive means to vary the characteristic of the strand-like material in a direction opposite to that of the first direction until the characteristic of the material no longer deviates beyond the first predetermined value, and responsive to the actuation of said second switch for causing said drive means to vary the characteristic of the material in a direction opposite to that of said second direction until the characteristic of the material no longer deviates beyond the second predetermined value, whereby said first and second switch responsive means operate to confine the variation in the characteristic of the material between said first and second predetermined values, said first and second switch responsive means including:

i. a bi-directional stepping motor having a shaft output drive, said shaft turning in a first rotational direction in response to actuation of said first switch and in a second rotational direction in response to actuation of said second switch;

ii. speed control means coupled to and controlling the speed of said drive means; and

iii. means mechanically coupled to said shaft for varying the operation of said speed control means.

7. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 6, wherein said motor includes a first winding in series with said first switch and a second winding in series with said second switch.

8. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 7 further including a first limit switch in series with said first winding and said first pressure sensitive switch, and a second limit switch in series with said second winding and said second pressure sensitive switch.

9. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 8 further including a timer operated switch in series with said first and second windings, said timer operated switch sequentially opening and closing to allow said motor shaft to rotate for an incremental step when said timer operated switch closes and for an additinal incremental step when said timer operated switch opens whenever either of said first pressure sensitive switch and limit switch or said second pressure sensitive switch and limit switch are actuated.

10. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 8, wherein said mechanically coupled means includes a potentiometer having an input shaft mechanically coupled to said motor shaft, and a disc mounted on said potentiometer shaft, said disc having a first and a second mechanical stop positioned thereon to engage and deactuate said first and second respective limit switches and thereby deactuate said motor to prevent said motor shaft from turning said potentiometer shaft beyond the points determined by the posiprevent the destruction of said potentiometer. 

1. Apparatus for controlling variation and a characteristic of continuously moving strand-like material comprising: a. means for fluidically monitoring the characteristic of the strand-like material passing therethrough; b. a fluidic bridge responsive to said monitoring means for producing a first pressure signal from a first output when the monitored characteristic of the strand-like material deviates beyond a first predetermined value in a first direction; c. a first pressure sensitive electrical switch fluidically coupled to said first output of said fluidic bridge and being actuated only in response to and for the duration of said first pressure signal; d. drive means engaging the strand-like material; and e. means responsive to the actuation of said first switch for causing said drive means to vary the characteristic of the strand-like material in a direction opposite to that of the first direction until the characteristic of the material no longer deviates beyond the first predetermined value, whereby said first pressure signal ceases, causing said first switch to become deactivated and said drive means to cease varying the characteristic of the material, said responsive means including: i. a motor having a shaft output drive, said shaft turning in a first rotational direction in response to actuation of said first switch; ii. speed control means coupled to and controlling the speed of said drive means; and iii. electrical means mechanically coupled to said shaft for varying the operation of said speed control means.
 2. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 1 wherein said motor includes a field winding in series with said first switch.
 3. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 2 further including a limit switch in series with said winding and said first switch.
 4. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 3, wherein said electrical means includes a potentiometer having an input shaft mechanically coupled to said motor shaft.
 5. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 4 further including: a. a disc mechanically coupled to the movement of said motor shaft, said disc having a mechanical stop positioned thereon to engage and deactivate said limit switch and thereby deactivate said motor to prevent said motor shaft from turning said potentiometer shaft beyond a point determined by the position of said mechanical stop so as to prevent destruction of said potentiometer.
 6. Apparatus for controlling variation in a characteristic of continuously moving strand-like material comprising: a. means for fluidically monitoring the characteristic of the strand-like material passing therethrough; b. a fluidic bridge responsive to said monitoring means for producing a first pressure signal from a first output when the monitored characteristic of the strand-like material deviates beyond a first predetermined value in a first direction, and for producing a second pressure signal from a second output when the monitored characteristic of the strand-like material deviates beyond a seconD predetermined value in a second direction; c. a first pressure sensitive electrical switch fluidically coupled to said first output of said fluidic bridge and being actuated only in response to and for the duration of said first pressure signal; d. a second pressure sensitive electrical switch fluidically coupled to said second output of said fluidic bridge and being actuated only in response to and for the duration of said second pressure signal; e. drive means engaging the strand-like material; and f. means responsive to the actuation of said first switch for causing said drive means to vary the characteristic of the strand-like material in a direction opposite to that of the first direction until the characteristic of the material no longer deviates beyond the first predetermined value, and responsive to the actuation of said second switch for causing said drive means to vary the characteristic of the material in a direction opposite to that of said second direction until the characteristic of the material no longer deviates beyond the second predetermined value, whereby said first and second switch responsive means operate to confine the variation in the characteristic of the material between said first and second predetermined values, said first and second switch responsive means including: i. a bi-directional stepping motor having a shaft output drive, said shaft turning in a first rotational direction in response to actuation of said first switch and in a second rotational direction in response to actuation of said second switch; ii. speed control means coupled to and controlling the speed of said drive means; and iii. means mechanically coupled to said shaft for varying the operation of said speed control means.
 7. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 6, wherein said motor includes a first winding in series with said first switch and a second winding in series with said second switch.
 8. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 7 further including a first limit switch in series with said first winding and said first pressure sensitive switch, and a second limit switch in series with said second winding and said second pressure sensitive switch.
 9. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 8 further including a timer operated switch in series with said first and second windings, said timer operated switch sequentially opening and closing to allow said motor shaft to rotate for an incremental step when said timer operated switch closes and for an additinal incremental step when said timer operated switch opens whenever either of said first pressure sensitive switch and limit switch or said second pressure sensitive switch and limit switch are actuated.
 10. Apparatus for controlling variation in a characteristic of continuously moving strand-like material according to claim 8, wherein said mechanically coupled means includes a potentiometer having an input shaft mechanically coupled to said motor shaft, and a disc mounted on said potentiometer shaft, said disc having a first and a second mechanical stop positioned thereon to engage and deactuate said first and second respective limit switches and thereby deactuate said motor to prevent said motor shaft from turning said potentiometer shaft beyond the points determined by the positions of said first and second mechanical stops so as to prevent the destruction of said potentiometer. 